#include<stdio.h>
int main()
{
	int n= 3;
    int shu =2*n;
    int a = 1;
    int b = 1;
    for (int i = 1; i <= n; i++)
    {
        a *=shu;
        shu--; 
        b*=i;
    }
    int zi= a/b;
    int mu = n+1;
    int jie= zi/mu;
	printf("%d",jie);
} 


